The present invention relates to a method for producing a palladium-phosphine complex compound, which is useful as a catalyst of organic synthesis.
Hitherto, various transition metal complexes have been used as catalysts of organic synthesis. In particular, noble metal complexes are stable and easy to handle. Thus, they are widely used as catalysts for organic synthesis, although they are high in price. Of optically active ligands of transition metal complexes used in asymmetric catalytic reactions, a ligand of 2,2′-bis(diphenylphosphino)-1,1′-binaphtyl (hereinafter referred to as “BINAP”) is one of the most superior ligands in asymmetry differentiation capability. It has been reported in J. Am. Chem. Soc., 1991, Vol. 118, pp. 1417 and J. Org. Chem., 1989, Vol. 54, pp. 4738 that a palladium complex having a ligand of BINAP is very much superior in catalytic activity, particularly in enantio-selectivity, for Heck reaction to an olefin, which is an asymmetric carbon-carbon bond formation reaction. In such reaction, there is assumed an involvement of an intermediate of [PhPd(I)(BINAP)], which is formed by an oxidative addition of benzene iodide to Pd(0)-BINAP formed in the reaction system.
There are known palladium complex compounds having ligands of trifluoromethylphenyl and tris(trifluoromethyl)phenyl, which are represented by the general formulas: where Y is fluorine, chlorine, bromine, or iodine.
J. Organomet. Chem., 1971, 28, 287 discloses a method for producing a palladium complex compound represented by the general formula Ar1Pd(PPh3)2X1 where Ar1 represents an aryl and X1 is a halogen. In this method, a stable palladium complex Pd0(PPh3)4 is reacted with an aryl halide. J. Organometallics, 1996, 15(17), 3708 discloses a similar method in which a palladium complex Pd2(dba)3 is used.
J. Chem. Commun., 1994, 121 discloses a reaction of dibromobis(triphenylphosphine)palladium(II) with toluene in the presence of potassium carbonate at 130° C. for 1 hr to obtain a small amount of bromo [methylphenyl]bis(triphenylphosphine)palladium(II).
J. Am. Chem. Soc., Vol. 117, No. 15, 4305 (1995) discloses a method for producing a palladium complex compound having a benzoato ligand, represented by the formula (Ph3P)2PdPh(PhCOO). In this method, (Ph3P)2Pd2Ph2(μ—OH)2 is dispersed in benzene. Then, benzoic acid is added to the mixture to have a solution having a pale yellow color. Then, the solvent is distilled away. After that, n-hexane is added, thereby obtaining (Ph3P)2Pd2Ph2(μ—PhCOO)2 in the form of crystal. The obtained crystals are dispersed in benzene. Then, triphenylphosphine is added, thereby preparing a transparent solution. Then, the solvent is distilled away. After that, n-hexane is added, thereby obtaining the aimed palladium complex compound in the form of crystal.
J. Oraganomet. Chem. 553 (1998) 83-90 discloses a method for producing trans-[Pd(OOC—(C6H4)-2—SMe—κ1—O)Ph(PPh3)2]. In this method, a thallium salt 2-RS—C6H4—COOTl is prepared by reacting 2—RS—C6H4—COOH with thallium carbonate in ethanol. Then, the thallium salt is reacted with trans-[PdCl(Ph)(PPh3)2] in tetrahydrofuran, thereby obtaining the product with a precipitate of thallium chloride.